The present invention relates to a crane return system for returning a crane to a home position upon loss of power to the crane.
Conventional overhead cranes include a frame with a pair of bridge cross members that move along a pair of main support beams. A pair of rails are supported by the cross members and a hoist moves along the pair of rails in a direction transverse to the main support beams. Some cranes are used to store and retrieve spent fuel bundles and containers holding radioactive materials or other hazardous materials. Often, the containers are stored within cells and tunnels inside a mountain or other facility and the crane transports the containers to and from storage positions. These high or low level radiation areas cannot be entered by humans and often there is a barrier sealing the tunnel. Once the crane passes the barrier, it may become stranded due to power failure, power loss to the crane, or failure of a component within the crane. In such a state, the crane is unreachable to repair due to the hazardous nature of the tunnels. To fix the crane, the load should be moved to an area where it can be lowered and the crane must be returned to a home position where it can be repaired.
One retrieval solution uses a rope or chain, with one end attached to the crane and another end located outside the barrier, to pull the crane back to a home position or a position outside the barrier where repairs can occur. However, due to the tunnel length, use of a rope to pull the crane back is not feasible or efficient. Further, the crane may not be able to roll back to the barrier because of the power loss. Another solution uses another device that moves along the rails to retrieve the crane, however, this solution is also limited if the crane cannot roll due to power loss.